Two sound posts??

Tony F · #1 09-01-2008, 08:06 PM

I thought I should finally ask some advice on this one.

I have a Leon Aubert R-21 laminated bass, which I bought from a member on this forum about a year ago. The bass is about four years old, and I'm very happy with it. One thing that has always puzzled me is the fact that it has TWO sound posts fitted - one conventional one, and one made from a strip of wood with a rectangular cross section, maybe 1" by 1/2" (from memory, I don't have the bass to hand as I type this).

The sound posts are fitted with one (the normal one) lower than the foot of the bridge, and the other one several inches above. You can sort of see what I'm talking about here -

So, is there a good reason why I have two sound posts? Are there any other Leon Aubert R-21 owners who can comment? Also, of course, is there anything stopping me asking my local luthier to remove one and give me a more conventional setup?

Thanks in advance,

Tony

oscar pettiford · #2 09-02-2008, 03:36 AM

how extraordinary!! !

ive never seen that before , maybe some structural function.....
. ...maybe someone was thinking 'the more the better '... dunno ? ....very strange

....
have a closer look , there might be some more in there ! ... ha

...seriously ,...
i really think one is enough

................................ . . . . . . . ..how extraordinary!!

oscar

toman · #3 09-02-2008, 04:14 AM

Not only a second post, but a rectangular one? If I received a bass like that I'd assume it was a joke!

Anything else odd about the bass? Is the bassbar normal (or present)? I can't quite tell from the photo, but is the upper post in line with the lower, or is it farther out, under the "wing" of the ff?

Strange...

Tony F · #4 09-02-2008, 05:27 AM

Quote:

Originally Posted by toman

Not only a second post, but a rectangular one? If I received a bass like that I'd assume it was a joke!

Anything else odd about the bass? Is the bassbar normal (or present)? I can't quite tell from the photo, but is the upper post in line with the lower, or is it farther out, under the "wing" of the ff?

Strange...

The bassbar is present, and quite normal! The only other thing slightly 'odd' about the bass is that if you look through the ff hole you can see that the top of the endpin has been drilled, with a split pin inserted so you can't remove it. Thanks guys, I'm so glad you did that for me...

I'll try to get a better look at the sound posts(!) and post a diagram of exactly where they're located relative to the bridge foot.

Cheers,

Tony

drurb · #5 09-02-2008, 07:29 AM

You can always go on tour with this guy.

**Damon Rondeau** · #6 09-02-2008, 11:54 AM

I'm far from an expert, but don't the basics go something like this: in violin instruments, the sound post "fixes" the vibration of the top plate -- it's a fixed nodal point and the plate vibrates around it. You move that nodal point around, you change the vibrating characteristics of the plate in-use -- that's why soundpost adjustments can change the sound of the instrument. If you've got two posts, set up the way yours appear to be, wouldn't that just make for a grossly bigger nodal point? It's got to have a significant effect on the sound, I would guess...

But there's no federal, state or municipal law that says two posts are verboten... How does the instrument sound? How does it sound in comparison with one post? What's stopping somebody from putting 10 posts in there?

Highly unusual indeed. I don't think we've seen that before in my time hanging at TalkBass...

Rebop · #7 09-02-2008, 12:23 PM

Funny, I once "repaired" a DB by placing a second soundpost inside it. However this was due to the bass having been shattered in a car accident, put back together and then developing multiple structural problems later on. The whole top of the bass creaked and rattled when played so I put the second post beneath the spider-web of glued up shards just as a temporary solution. Didn't change the sound or character of the bass; although it had already been severely compromised by the damage.

sXeMike · #8 09-02-2008, 01:46 PM

I've heard of adding a second soundpost to fight feedback in an amplified rig.

Tony, do you still use rockabillybass.com? I haven't seen you post in a while

drurb · #9 09-02-2008, 02:11 PM

Quote:

Originally Posted by Damon Rondeau

...If you've got two posts, set up the way yours appear to be, wouldn't that just make for a grossly bigger nodal point?

Not really. Depending upon their distance from each other, it could create two nodal points. I can't imagine that the Chladni patterns would be anywhere near optimal with two posts.

**Damon Rondeau** · #10 09-02-2008, 02:25 PM

Sure, but those posts are really close together. What, 4 or 5 inches? There ain't nothing happening in that space.

The (highly) amplified rig thing makes theoretical sense -- feedback is controlled because the top's vibration is reduced.

Rebop · #11 09-02-2008, 02:38 PM

Quote:

Originally Posted by Damon Rondeau

The (highly) amplified rig thing makes theoretical sense -- feedback is controlled because the top's vibration is reduced.

I've only had success with that by dampening near the bass bar somehow. At least with my bass, at Jimi Hendrix volume, the bass side is where all my feedback comes from. But that's just my bass.

sXeMike · #12 09-02-2008, 02:53 PM

Quote:

Originally Posted by Rebop

I've only had success with that by dampening near the bass bar somehow. At least with my bass, at Jimi Hendrix volume, the bass side is where all my feedback comes from. But that's just my bass.

The 2 double-posted basses that I've seen had a post under each bridge foot. Neither one sounded very good and they would still get some crazy feedback. (The rest of their setup sucked)

How does it sound Mr. F? If it sounds good, why change it? Then-again, maybe it will sound better with one post...

**Damon Rondeau** · #13 09-02-2008, 02:55 PM

Like I said, I'm not sure many of us have seen this before, I'm no expert, and I'm working from theory here. Given that: dampening near the bass bar to control feedback continues to make theoretical sense, as the bass bar is the driver of the top.

There used to be a link on Bob Gollihur's site, I think, to an animation showing in exaggerated motion how the top moves when it's in action. You can see the bass bar pumping away and the top moving around that soundpost nodal point.

**Damon Rondeau** · #14 09-02-2008, 02:58 PM

Here's another thought: that soundpost that's north of the bridge seems to be located pretty close to an f-hole wing. If the post isn't fit really well, and if the bass gets a whack from behind in just the right spot, wouldn't you stand a good chance of saying bye-bye to the wing?

Rebop · #15 09-02-2008, 03:02 PM

Honestly, if it were my bass, that second post wouldn't have lasted 5 minutes.

drurb · #16 09-02-2008, 06:07 PM

Quote:

Originally Posted by Damon Rondeau

Sure, but those posts are really close together. What, 4 or 5 inches? There ain't nothing happening in that space.

Really? Trust me, it's reasonably complicated and is, of course, highly dependent upon the frequencies being radiated.

Tony F · #17 09-02-2008, 09:05 PM

I've had another look at this bass, and taken a ruler to the front of the bass. These pics should show roughly where the soundposts are. I'd say that the bottom post is maybe 3" south of the ff hole nick, and the smaller post is 2.5 inches above.

The sound is certainly clear and tight, and louder than my old Czech ply (although that had a lot of not-so-subtle repairs and patches inside).

When amped I find the sound very "live", lots of bright tones and string noise. I use an Underwood pickup and Rotosound strings at the moment, and I've certainly not played at any high volumes.

Right now I'm interested in setting up my bass for jazz, and was wondering if a single soundpost would go some way to getting the rich "growly" kind of sound I've got in my head... Obviously a better bass (hybrid, perhaps) would be a big step forward, but right now I am enjoying this bass and the sound is certainly loud (but not boomy and unfocused).

Cheers,

Tony

drurb · #18 09-02-2008, 09:13 PM

Quote:

Originally Posted by Rebop

Honestly, if it were my bass, that second post wouldn't have lasted 5 minutes.

+1.

Let's face it. Unless that second post was added to redress some structural problem, it doesn't belong there. I think we can rely on hundreds of years of the design of these instruments. I suggest you take the bass to a qualified luthier.

GerardSamija · #19 09-03-2008, 01:00 AM

I'll add my concurrence with that last, and earlier comments to the effect that it ought to go. One post is enough, and would seem to make adjusting the sound of the instrument with the remaining 'proper' soundpost a lot more predictable.

My guess insofar as the function of the rectangular post goes is that this top is rather thin and weak, and as such has shown a tendency for the upper wing on the post side to become significantly deformed, down into the bass, owing to pressure from the bridge. The post which resides in the more traditional location is very, very far South of the bridge, especially so if the top is as thin and weak as my suspicions lead me to think. Many a thin-topped ply bass has a hump above the soundpost when it's been left sitting more than about 1 soundpost diameter away for more than a few years. A lot of early Kay basses, the ones with the thinner (and more responsive) tops are like that. So are a lot of Epiphones and other ply instruments. Happens on steam-formed solid spruce bellies like those of the Santini line from Korea as well, where a thin, flat panel of spruce has been steamed and formed over a mould. Those start deforming from the moment they're first strung up, but they're also quite 'boomy' so I guess it's what some players want.

Anyway, I'd get that lower post closer to the bridge while maintaining it's left-to-right position, remove the upper one (if it's not glued in!), and try it to see how the sound changed. Also consider first making a template of card, across the upper wing on that f-hole. Then compare that template to the same area after removing the upper post and bringing the bass up to pitch, before moving the lower post. Record any differences, then do this a third time once the post has been brought to within less than an inch of the bridge foot's lower edge. My guess is that you will see three different deflections of that wing, and to really step out on a limb here... I'll guess that the difference between step 1 and 2 will be about 3mm or a bit more.